For the formation of a functional deposited film, particularly a semiconductor deposited film, there has been employed a suitable film-forming process with due regards to electrical and physical properties required therefor and also to its application use.
For example, there have been attempted plasma CVD process, reactive sputtering process, ion plating process, light CVD process, thermal-induced CVD process, MO CVD process, MBE process, etc. and several of which have been employed and put to industrial use as being suitable for the formation of a desired semiconductor device.
However, even in the case of the plasma CVD process which has been employed most popularly, the electrical and physical properties of a resulting deposited film are not said quite satisfactory in view of the preparation of a desired semiconductor device and it sometime lacks in the plasma stability and reproducibility upon forming the deposited film and in addition, it may sometime cause a remarkable reduction in the yield.
For overcoming these problems, there has been proposed, for example, by Japanese Patent Laid-Open Sho 61-189649 and Sho 61-189650, a process for increasing the film deposition rate thereby remarkably improving the productivity of the film upon depositing to form a group III - V semiconductor film of high quality by HR-CVD process (Hydrogen Radical Assisted CVD process).
Further, as means for forming a high density plasma efficiently by using microwaves of about 2.45 GHz, a method for arranging electromagnets around a cavity resonator thereby establishing conditions for ECR (electron cyclotron resonance) has been proposed, for example, by Japanese Patent Laid-Open Sho 55-141729 and Sho 57-133636. In addition, formation of various kinds of semiconductor thin films by utilizing high density plasma has also been reported in academic conferences, etc.
By the way, in the HR-CVD process described above, although the hydrogen atoms in excited state (hydrogen radicals) have an important role for the formation of a deposited film regarding the control of the film property and the uniformity, there has been made no sufficient study for controlling the excited state of the hydrogen atoms in a great amount and uniformly upon forming the deposited film and controlling the chemical reaction upon forming the deposited film under the control of the excited state, thereby optionally and stably controlling the property of the deposited film formed, and there are still left several problems to be solved.
On the other hand, in the microwave plasma CVD apparatus using ECR, there are several problems. That is: the pressure in a plasma generation chamber has to be kept to less than about 10.sup.-3 Torr for establishing ECR conditions, thus undergoing restriction for the pressure upon forming the deposited film: the mean free path of gaseous molecules is increased (.about.1 m) under such a level of pressure, by which the film-forming raw material gas is diffused near the microwave introduction window, decomposed and reacted to thereby cause adherence of the deposited film to the microwave introduction window or to the inner wall of the cavity resonator, thereby making electric discharge instable: and the film adhered to the substrate is contaminated by the defoliation and the scattering of the adhered film. Further, it has also been pointed out several problems. That is, a plasma generated in the plasma generation chamber is diversed along the diversing magnetic field of the electromagnets into the film forming chamber, by which the substrate is exposed to the plasma at relatively high density. Accordingly, the formed deposited film is liable to be damaged by charged particles, etc. and this causes limitation in the improvement of properties of a film to be formed. In the step of laminating a plurality of deposited films in the process of preparing a semiconductor device, the boundary characteristic is apt to reduce because of damages caused by the charged particles, etc., and this makes it difficult to improve the characteristics of the semiconductor device.